Modern thrust generation devices are inefficient and generate significant emissions. Propulsion devices such as the internal combustion engine only operate at about 20%-40% mechanical efficiency and rely almost entirely on fossil fuels. Further, these engines emit a variety of harmful emissions, such as carbon monoxide and other greenhouse gases. Additionally, these engines are not capable of generating significant amounts of thrust or power over prolonged periods without mechanical failure or without exhaust their fuel supply.
Other propulsion devices, such as jet engines, are capable of producing much greater amounts of thrust and, often, greater thrust over a greater amount of time. For example, jet engines are well known to propel aircraft to several times the speed of sound and propel space craft beyond Earth's atmosphere. Jet engines, however, are also limited by their prodigious fuel consumption and typically require exotic fuel mixtures or types or extremely volatile or difficult to store fuels. Jet engines also produce an immense amount of emissions. Thus, while jet engines are capable of generating significant amounts of thrust, they are often limited in the amount of time or distance that they can travel due to the fuel load that they must carry and support. Additionally, the weight of the fuel is often a significant problem when a vessel having one or more jet engines first attempts to propel itself under its own power.
Still other propulsion devices, such as nuclear powered engines, have the capability to produce thrust for significant amounts of time. These engines, however, require a party to have nuclear capabilities in order to first obtain the fuel and then produce the engine. Additionally the potential drawbacks of nuclear power are well known and are not suitable or feasible for most applications where propulsion is desired.